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Re: [PATCH 4/4] riscv: Add semihosting support [v11]
|
From: |
Keith Packard |
|
Subject: |
Re: [PATCH 4/4] riscv: Add semihosting support [v11] |
|
Date: |
Wed, 11 Nov 2020 14:49:34 -0800 |
Alistair Francis <alistair23@gmail.com> writes:
>> + return (nr == TARGET_SYS_EXIT_EXTENDED || sizeof(target_ulong) == 0);
>
> How would sizeof(target_ulong) == 0 ?
Oops. This is supposed to be 8, not 0. And those look very similar on
the screen. I caught this myself a couple of weeks ago but forgot to
send out a new version here. Sorry!
From a6cb1a52a6c2404a9bdc22bb5e00bccb65ab0730 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Mon, 26 Oct 2020 12:20:01 -0700
Subject: [PATCH 4/4] riscv: Add semihosting support [v12]
Adapt the arm semihosting support code for RISCV. This implementation
is based on the standard for RISC-V semihosting version 0.2 as
documented in
https://github.com/riscv/riscv-semihosting-spec/releases/tag/0.2
Signed-off-by: Keith Packard <keithp@keithp.com>
---
v2:
Update PC after exception is handled to follow
change in the ARM version for SYS_READC
v3:
Disallow semihosting in user mode; report a regular
breakpoint in that case.
v4:
Fix errors reported by checkpatch
v5:
Reference current RISC-V semihosting specification
v6:
Add support for semihosting in riscv64-linux-user and
riscv32-linux-user
v7:
Add meson build support
v8:
Fix errors reported by checkpatch that crept in.
v9:
Changes suggested by Alistair Francis <alistair23@gmail.com>:
Don't add me to the MAINTAINERS file.
Remove duplicate #include in target/riscv/cpu.h
Reference RISC-V semihosting spec in target/riscv/riscv-semi.c
v10:
Use common semihosting implementation instead of a separate copy.
Make sure addresses of the three breakpoint-signaling
instructions all lie within the same page. Change suggested by
Richard Henderson <richard.henderson@linaro.org>
v11:
Use CONFIG_ARM_COMPATIBLE_SEMIHOSTING
v12:
Fix bug in SYS_EXIT support on rv64
---
default-configs/devices/riscv32-softmmu.mak | 2 +
default-configs/devices/riscv64-softmmu.mak | 2 +
.../targets/riscv32-linux-user.mak | 1 +
.../targets/riscv64-linux-user.mak | 1 +
hw/semihosting/common-semi.c | 51 ++++++++++++++++++-
hw/semihosting/common-semi.h | 5 +-
linux-user/qemu.h | 4 +-
linux-user/semihost.c | 8 +--
qemu-options.hx | 10 ++--
target/riscv/cpu_bits.h | 1 +
target/riscv/cpu_helper.c | 10 ++++
.../riscv/insn_trans/trans_privileged.c.inc | 37 +++++++++++++-
target/riscv/translate.c | 11 ++++
13 files changed, 131 insertions(+), 12 deletions(-)
diff --git a/default-configs/devices/riscv32-softmmu.mak
b/default-configs/devices/riscv32-softmmu.mak
index 94a236c9c2..d847bd5692 100644
--- a/default-configs/devices/riscv32-softmmu.mak
+++ b/default-configs/devices/riscv32-softmmu.mak
@@ -3,6 +3,8 @@
# Uncomment the following lines to disable these optional devices:
#
#CONFIG_PCI_DEVICES=n
+CONFIG_SEMIHOSTING=y
+CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
# Boards:
#
diff --git a/default-configs/devices/riscv64-softmmu.mak
b/default-configs/devices/riscv64-softmmu.mak
index 76b6195648..d5eec75f05 100644
--- a/default-configs/devices/riscv64-softmmu.mak
+++ b/default-configs/devices/riscv64-softmmu.mak
@@ -3,6 +3,8 @@
# Uncomment the following lines to disable these optional devices:
#
#CONFIG_PCI_DEVICES=n
+CONFIG_SEMIHOSTING=y
+CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
# Boards:
#
diff --git a/default-configs/targets/riscv32-linux-user.mak
b/default-configs/targets/riscv32-linux-user.mak
index dfb259e8aa..6a9d1b1bc1 100644
--- a/default-configs/targets/riscv32-linux-user.mak
+++ b/default-configs/targets/riscv32-linux-user.mak
@@ -2,3 +2,4 @@ TARGET_ARCH=riscv32
TARGET_BASE_ARCH=riscv
TARGET_ABI_DIR=riscv
TARGET_XML_FILES= gdb-xml/riscv-32bit-cpu.xml gdb-xml/riscv-32bit-fpu.xml
gdb-xml/riscv-64bit-fpu.xml gdb-xml/riscv-32bit-csr.xml
gdb-xml/riscv-32bit-virtual.xml
+CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
diff --git a/default-configs/targets/riscv64-linux-user.mak
b/default-configs/targets/riscv64-linux-user.mak
index b13895f3b0..0a92849a1b 100644
--- a/default-configs/targets/riscv64-linux-user.mak
+++ b/default-configs/targets/riscv64-linux-user.mak
@@ -2,3 +2,4 @@ TARGET_ARCH=riscv64
TARGET_BASE_ARCH=riscv
TARGET_ABI_DIR=riscv
TARGET_XML_FILES= gdb-xml/riscv-64bit-cpu.xml gdb-xml/riscv-32bit-fpu.xml
gdb-xml/riscv-64bit-fpu.xml gdb-xml/riscv-64bit-csr.xml
gdb-xml/riscv-64bit-virtual.xml
+CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
diff --git a/hw/semihosting/common-semi.c b/hw/semihosting/common-semi.c
index c77fb21bec..f8c5d04732 100644
--- a/hw/semihosting/common-semi.c
+++ b/hw/semihosting/common-semi.c
@@ -1,6 +1,6 @@
/*
* Semihosting support for systems modeled on the Arm "Angel"
- * semihosting syscalls design.
+ * semihosting syscalls design. This includes Arm and RISC-V processors
*
* Copyright (c) 2005, 2007 CodeSourcery.
* Copyright (c) 2019 Linaro
@@ -25,6 +25,10 @@
* ARM Semihosting is documented in:
* Semihosting for AArch32 and AArch64 Release 2.0
* https://static.docs.arm.com/100863/0200/semihosting.pdf
+ *
+ * RISC-V Semihosting is documented in:
+ * RISC-V Semihosting
+ *
https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc
*/
#include "qemu/osdep.h"
@@ -163,6 +167,30 @@ common_semi_sys_exit_extended(CPUState *cs, int nr)
}
#endif /* TARGET_ARM */
+#ifdef TARGET_RISCV
+static inline target_ulong
+common_semi_arg(CPUState *cs, int argno)
+{
+ RISCVCPU *cpu = RISCV_CPU(cs);
+ CPURISCVState *env = &cpu->env;
+ return env->gpr[xA0 + argno];
+}
+
+static inline void
+common_semi_set_ret(CPUState *cs, target_ulong ret)
+{
+ RISCVCPU *cpu = RISCV_CPU(cs);
+ CPURISCVState *env = &cpu->env;
+ env->gpr[xA0] = ret;
+}
+
+static inline bool
+common_semi_sys_exit_extended(CPUState *cs, int nr)
+{
+ return (nr == TARGET_SYS_EXIT_EXTENDED || sizeof(target_ulong) == 8);
+}
+#endif
+
/*
* Allocate a new guest file descriptor and return it; if we
* couldn't allocate a new fd then return -1.
@@ -339,6 +367,12 @@ static target_ulong common_semi_flen_buf(CPUState *cs)
sp = env->regs[13];
}
#endif
+#ifdef TARGET_RISCV
+ RISCVCPU *cpu = RISCV_CPU(cs);
+ CPURISCVState *env = &cpu->env;
+
+ sp = env->gpr[xSP];
+#endif
return sp - 64;
}
@@ -678,6 +712,18 @@ static const GuestFDFunctions guestfd_fns[] = {
put_user_u32(val, args + (n) * 4))
#endif
+#ifdef TARGET_RISCV
+#define GET_ARG(n) do { \
+ if (get_user_ual(arg ## n, args + (n) * sizeof(target_ulong))) { \
+ errno = EFAULT; \
+ return set_swi_errno(cs, -1); \
+ } \
+ } while (0)
+
+#define SET_ARG(n, val) \
+ put_user_ual(val, args + (n) * sizeof(target_ulong))
+#endif
+
/*
* Do a semihosting call.
*
@@ -1112,6 +1158,9 @@ target_ulong do_common_semihosting(CPUState *cs)
if (is_a64(cs->env_ptr)) {
return 0;
}
+#endif
+#ifdef TARGET_RISCV
+ return 0;
#endif
/* fall through -- invalid for A32/T32 */
default:
diff --git a/hw/semihosting/common-semi.h b/hw/semihosting/common-semi.h
index bc53e92c79..0bfab1c669 100644
--- a/hw/semihosting/common-semi.h
+++ b/hw/semihosting/common-semi.h
@@ -1,6 +1,6 @@
/*
* Semihosting support for systems modeled on the Arm "Angel"
- * semihosting syscalls design.
+ * semihosting syscalls design. This includes Arm and RISC-V processors
*
* Copyright (c) 2005, 2007 CodeSourcery.
* Copyright (c) 2019 Linaro
@@ -26,6 +26,9 @@
* Semihosting for AArch32 and AArch64 Release 2.0
* https://static.docs.arm.com/100863/0200/semihosting.pdf
*
+ * RISC-V Semihosting is documented in:
+ * RISC-V Semihosting
+ *
https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc
*/
#ifndef COMMON_SEMI_H
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 534753ca12..17aa992165 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -109,6 +109,8 @@ typedef struct TaskState {
/* FPA state */
FPA11 fpa;
# endif
+#endif
+#if defined(TARGET_ARM) || defined(TARGET_RISCV)
int swi_errno;
#endif
#if defined(TARGET_I386) && !defined(TARGET_X86_64)
@@ -122,7 +124,7 @@ typedef struct TaskState {
#ifdef TARGET_M68K
abi_ulong tp_value;
#endif
-#if defined(TARGET_ARM) || defined(TARGET_M68K)
+#if defined(TARGET_ARM) || defined(TARGET_M68K) || defined(TARGET_RISCV)
/* Extra fields for semihosted binaries. */
abi_ulong heap_base;
abi_ulong heap_limit;
diff --git a/linux-user/semihost.c b/linux-user/semihost.c
index a1f0f6050e..c0015ee7f6 100644
--- a/linux-user/semihost.c
+++ b/linux-user/semihost.c
@@ -1,11 +1,11 @@
/*
- * ARM Semihosting Console Support
+ * ARM Compatible Semihosting Console Support.
*
* Copyright (c) 2019 Linaro Ltd
*
- * Currently ARM is unique in having support for semihosting support
- * in linux-user. So for now we implement the common console API but
- * just for arm linux-user.
+ * Currently ARM and RISC-V are unique in having support for
+ * semihosting support in linux-user. So for now we implement the
+ * common console API but just for arm and risc-v linux-user.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
diff --git a/qemu-options.hx b/qemu-options.hx
index 2c83390504..9a606946c4 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4184,10 +4184,10 @@ ERST
DEF("semihosting", 0, QEMU_OPTION_semihosting,
"-semihosting semihosting mode\n",
QEMU_ARCH_ARM | QEMU_ARCH_M68K | QEMU_ARCH_XTENSA | QEMU_ARCH_LM32 |
- QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2)
+ QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2 | QEMU_ARCH_RISCV)
SRST
``-semihosting``
- Enable semihosting mode (ARM, M68K, Xtensa, MIPS, Nios II only).
+ Enable semihosting mode (ARM, M68K, Xtensa, MIPS, Nios II, RISC-V only).
Note that this allows guest direct access to the host filesystem, so
should only be used with a trusted guest OS.
@@ -4199,10 +4199,10 @@ DEF("semihosting-config", HAS_ARG,
QEMU_OPTION_semihosting_config,
"-semihosting-config
[enable=on|off][,target=native|gdb|auto][,chardev=id][,arg=str[,...]]\n" \
" semihosting configuration\n",
QEMU_ARCH_ARM | QEMU_ARCH_M68K | QEMU_ARCH_XTENSA | QEMU_ARCH_LM32 |
-QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2)
+QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2 | QEMU_ARCH_RISCV)
SRST
``-semihosting-config
[enable=on|off][,target=native|gdb|auto][,chardev=id][,arg=str[,...]]``
- Enable and configure semihosting (ARM, M68K, Xtensa, MIPS, Nios II
+ Enable and configure semihosting (ARM, M68K, Xtensa, MIPS, Nios II, RISC-V
only).
Note that this allows guest direct access to the host filesystem, so
@@ -4217,6 +4217,8 @@ SRST
open/read/write/seek/select. Tensilica baremetal libc for ISS and
linux platform "sim" use this interface.
+ On RISC-V this implements the standard semihosting API, version 0.2.
+
``target=native|gdb|auto``
Defines where the semihosting calls will be addressed, to QEMU
(``native``) or to GDB (``gdb``). The default is ``auto``, which
diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index daedad8691..6bd7bcb26d 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -545,6 +545,7 @@
#define RISCV_EXCP_INST_PAGE_FAULT 0xc /* since: priv-1.10.0 */
#define RISCV_EXCP_LOAD_PAGE_FAULT 0xd /* since: priv-1.10.0 */
#define RISCV_EXCP_STORE_PAGE_FAULT 0xf /* since: priv-1.10.0 */
+#define RISCV_EXCP_SEMIHOST 0x10
#define RISCV_EXCP_INST_GUEST_PAGE_FAULT 0x14
#define RISCV_EXCP_LOAD_GUEST_ACCESS_FAULT 0x15
#define RISCV_EXCP_VIRT_INSTRUCTION_FAULT 0x16
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 3eb3a034db..aa8e9ac9e4 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -24,6 +24,7 @@
#include "exec/exec-all.h"
#include "tcg/tcg-op.h"
#include "trace.h"
+#include "hw/semihosting/common-semi.h"
int riscv_cpu_mmu_index(CPURISCVState *env, bool ifetch)
{
@@ -862,6 +863,15 @@ void riscv_cpu_do_interrupt(CPUState *cs)
target_ulong htval = 0;
target_ulong mtval2 = 0;
+ if (cause == RISCV_EXCP_SEMIHOST) {
+ if (env->priv >= PRV_S) {
+ env->gpr[xA0] = do_common_semihosting(cs);
+ env->pc += 4;
+ return;
+ }
+ cause = RISCV_EXCP_BREAKPOINT;
+ }
+
if (!async) {
/* set tval to badaddr for traps with address information */
switch (cause) {
diff --git a/target/riscv/insn_trans/trans_privileged.c.inc
b/target/riscv/insn_trans/trans_privileged.c.inc
index 2a61a853bf..32312be202 100644
--- a/target/riscv/insn_trans/trans_privileged.c.inc
+++ b/target/riscv/insn_trans/trans_privileged.c.inc
@@ -29,7 +29,42 @@ static bool trans_ecall(DisasContext *ctx, arg_ecall *a)
static bool trans_ebreak(DisasContext *ctx, arg_ebreak *a)
{
- generate_exception(ctx, RISCV_EXCP_BREAKPOINT);
+ target_ulong ebreak_addr = ctx->base.pc_next;
+ target_ulong pre_addr = ebreak_addr - 4;
+ target_ulong post_addr = ebreak_addr + 4;
+ uint32_t pre = 0;
+ uint32_t ebreak = 0;
+ uint32_t post = 0;
+
+ /*
+ * The RISC-V semihosting spec specifies the following
+ * three-instruction sequence to flag a semihosting call:
+ *
+ * slli zero, zero, 0x1f 0x01f01013
+ * ebreak 0x00100073
+ * srai zero, zero, 0x7 0x40705013
+ *
+ * The two shift operations on the zero register are no-ops, used
+ * here to signify a semihosting exception, rather than a breakpoint.
+ *
+ * Uncompressed instructions are required so that the sequence is easy
+ * to validate.
+ *
+ * The three instructions are required to lie in the same page so
+ * that no exception will be raised when fetching them.
+ */
+
+ if ((pre_addr & TARGET_PAGE_MASK) == (post_addr & TARGET_PAGE_MASK)) {
+ pre = opcode_at(&ctx->base, pre_addr);
+ ebreak = opcode_at(&ctx->base, ebreak_addr);
+ post = opcode_at(&ctx->base, post_addr);
+ }
+
+ if (pre == 0x01f01013 && ebreak == 0x00100073 && post == 0x40705013) {
+ generate_exception(ctx, RISCV_EXCP_SEMIHOST);
+ } else {
+ generate_exception(ctx, RISCV_EXCP_BREAKPOINT);
+ }
exit_tb(ctx); /* no chaining */
ctx->base.is_jmp = DISAS_NORETURN;
return true;
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 79dca2291b..ecf594babc 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -63,6 +63,7 @@ typedef struct DisasContext {
uint16_t vlen;
uint16_t mlen;
bool vl_eq_vlmax;
+ CPUState *cs;
} DisasContext;
#ifdef TARGET_RISCV64
@@ -746,6 +747,15 @@ static bool gen_shift(DisasContext *ctx, arg_r *a,
return true;
}
+static uint32_t opcode_at(DisasContextBase *dcbase, target_ulong pc)
+{
+ DisasContext *ctx = container_of(dcbase, DisasContext, base);
+ CPUState *cpu = ctx->cs;
+ CPURISCVState *env = cpu->env_ptr;
+
+ return cpu_ldl_code(env, pc);
+}
+
/* Include insn module translation function */
#include "insn_trans/trans_rvi.c.inc"
#include "insn_trans/trans_rvm.c.inc"
@@ -812,6 +822,7 @@ static void riscv_tr_init_disas_context(DisasContextBase
*dcbase, CPUState *cs)
ctx->lmul = FIELD_EX32(tb_flags, TB_FLAGS, LMUL);
ctx->mlen = 1 << (ctx->sew + 3 - ctx->lmul);
ctx->vl_eq_vlmax = FIELD_EX32(tb_flags, TB_FLAGS, VL_EQ_VLMAX);
+ ctx->cs = cs;
}
static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu)
--
2.29.1
--
-keith
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